Okay, so at least I wasn’t the only one. I tried older versions of Z-Push 3.0->3.6 and also Webapp 3.4.0 and 3.30. The problem seems to be linked solely to Kopano Core. I can also confirm the iOS issues @MacusRieche

This kind of message usually occurs regarding the to field. For example for undisclosed recipients or or just my name as receiver. That is not nessecary right and was always kind of wrong, since I was cleary the recipient and nine mail on android seems to replace empty from fields with my own address this was never an issue. Missing sender information in the from field is an issue.

I can try to help to debug this issue in the next days, if you want me to take special steps.

@MarcusRieche that was my thought as well. If the error still persists either the webserver wasn’t restarted and the version of php-mapi is still in use or he is speaking about messages synced to mobile devices. The latter requires a resync.

@fbartels Resync didn’t helped (over Z-push right)? I have this problem after upgrading Kopano Core in mobile devices and WebApp. I restarted the entire Kopano Server after upgrade to ensure that everything is “fresh” loaded and this issue is still there. It’s also inconsistent . Some sender are not in WebApp but in mail Client (Nine Android). Some in the another direction.

Seems to be fixed for me with ,core-8.4.0~813_153.1-Ubuntu_16.04-amd64.tar.gz". Older messages has still the problem but new messages not more that sender is not visible or the error message ,Message coulnd’t be loaded" in WebApp.